Iodopropargyl compounds are known active ingredients which are used particularly in material protection for protecting technical materials such as adhesives, sizes, paper and cardboard, textiles, leather, wood, woodbase materials, coatings and plastic articles, cooling lubricants and other materials which can be attacked or decomposed by microorganisms against attack, particularly by fungi. The best known representative of the iodopropargyl compounds is iodopropargyl butylcarbamate, which is also referred to hereinbelow as IPBC.
High demands are placed on fungicides used for the finishing of coating compositions such as e.g. wood protection paints, exterior paints or plasters. For example, the fungicidally finished coating compositions have to remain stable even upon frequent contact with water and must not be subject to any undesired discolouration. Since some fungicides such as, for example, IPBC, have a certain solubility in water, as a result of contact of the exterior paint for example with driving rain, the fungicide is washed out of the paints. This process is also called “leaching”. It results in a reduction in the fungitoxic effect in the coating compositions as well as a severe local burden on the environment by the active ingredients or their metabolites. This leaching should be low so that the coating compositions and the exterior walls are protected against fungal attack for a long time. One option of reducing the leaching is to use microencapsulations.
Coating compositions protected against microbiological attack, and processes for producing microencapsulated biocides are known from the prior art.
Thus, for example, WO 04/000953A1 describes a coating composition for protecting against microorganism attack of surfaces which are subjected to the action of moisture or water, wherein the coating composition either itself has a pH of at least 11.0 or is intended for the coating of a substrate material whose pH is at least 11.0. The coating composition is characterized in that it comprises a biocide, such as e.g. IPBC, which is bonded in a carrier material made of solids particles and is released therefrom in a delayed manner.
DE102006061890 A1 describes sealing compositions which comprise, as biocide, for example 2-n-octyl-4-isothiazolin-3-one and optionally one or more other biocides, wherein the biocide is enclosed in microparticles made, for example, of an aminoplastic resin.
It is known from DE10133545 A1 to treat sealing compositions with special benzothiophene fungicide preparations in order to prevent the polymer masses from becoming mouldy. Reference is also made here to the difficulty of finding suitable fungicides for sealing compositions which are stable and are not subject to being washed out. Consequently, the biocides employed have to be used in high concentrations, which can also lead to an environmental impact.
It is known from JP2002-053412 A2 that biocides can be enclosed in a resin matrix. Thus, the inclusion of 2-n-octyl-4-isothiazolin-3-one in a styrene-maleic anhydride resin is described in this document,
EP 0 758 633 A1 describes porous granules which can comprise chemical substances, such as, for example, also biocides, which slowly release these during use.
JP2004039557 A2 describes fine particles of biocide-containing resin which are used for suppressing the growth of microorganisms especially in aqueous emulsion paints.
However, the microcapsules known from the prior art still have no satisfactory antifungal effect coupled with simultaneously low leaching rate and high resistance or storage stability.
It was therefore the object of the present invention to provide microcapsules which permit improved protection of coating compositions against fungal attack.